1. Field of the Invention
The present invention relates to an image forming apparatus provided with a stapler capable of performing stapling processing, for example, in arbitrary timing on a recording material with an image formed thereon, and a method for controlling power supply to the stapler.
2. Description of the Related Art
In image forming apparatuses such as a printer and a copying machine, an apparatus having a stapler for stapling an end part of a bundle of a plurality of sheets (printed recording materials) has been known. Further, an apparatus is known which can be separately provided with a stapler as an optional device to be connected to the image forming apparatus. A user can perform stapling of recording material sheets in arbitrary timing. To supply electric power to these staplers, for example, a power source provided with a dedicated adapter for converting commercial alternating current (AC) voltage into direct current (DC) voltage, or a power source that shares power with an image forming apparatus, and generates and supplies DC voltage from the power source are used.
In the former power source, since a dedicated power source for the stapler is provided, the power source is required to supply only electric power necessary for the stapler, and the design is easy. However in this case, since the power source is provided separately from the power source of the image forming apparatus, costs of the apparatus increase, or the size of the power source of the apparatus increases. This hinders reduction in costs or reduction in size. On the other hand, in the latter case, the power source of the image forming apparatus and the stapler is shared. Accordingly, as compared to the former case, the reduction in costs or the reduction in size can be easily achieved. In the latter case, however, if the stapling processing is performed in arbitrary timing, power supply timing control is necessary. For example, control has to be performed to prevent the timing of the stapling processing from overlapping with that of image forming operation in the image forming apparatus.
The stapler uses a direct current (DC) motor as a drive unit for operating a mechanism portion for stapling. By driving and rotating the DC motor, driving force is applied to a cam or a gear in the mechanism portion to perform the stapling. In such a stapler, for example, if an unusual condition such as an overcurrent occurs, in order to prevent damage in the power source circuit or the mechanism portion, or in order to reduce the power consumption, a circuit for limiting the current running through the DC motor to a constant value or less or a current interruption circuit for interrupting the current running in the stapler are provided. For example, Japanese Patent Application Laid-Open No. 2008-9112 proposes a configuration of sharing a power source of an image forming apparatus and connecting a current limiting circuit between a stapler and the power source. The power source is configured to control overcurrent such as inrush current using the current limiting circuit to respond flexibly to the load change.
In the above-described case, that is, in the configuration of sharing the power source of the image forming apparatus with the stapler, if the timing when the stapler operates is known in advance, it is easy to control or stop the operation. However, if the user executes the stapling processing in arbitrary timing, it is necessary to prevent the processing from overlapping with the image forming operation. To solve the problem, the following methods can be applied:
(1) separate the execution timings such that the stapling processing and the image forming operation are not simultaneously performed, or
(2) set a part of a time period for prohibiting the stapling processing (time period the load increases) in the image forming operation such that power consumption does not exceed the capacity of the power source.
In the method (1), if an instruction of implementing the stapling processing is issued in arbitrary timing, the current for the stapling processing may not be sufficient at the timing, and then, the stapling processing may be suspended. This may cause decrease in the productivity in the stapling processing. In the method (2), during the stapling processing, the operation may be prohibited. For example, if the operation is stopped in the middle of stapling, the staple may be stuck (occurrence of so-called staple jam).